Automated coagulation testing has been accomplished by apparatus developed in recent years. Thus, apparatus has been developed for testing plasma samples for prothrombin time, activated partial thromboplastin time, factor assays, and many other tests. Prior art devices have included means for pre-warming components in fluids and have utilized photoelectric systems for measuring coagulation time. In fact, such devices as the COAG-A-MATE single channel clot detection system sold by General Diagnostics Division of the Warner-Lambert Company has been very effective for such measurements. Devices for a similar purpose are manufactured by Medical Laboratory Automation, Inc. as the MLA Electra 620 and 600 Coagulation Timers. These devices have been described in U.S. Pat. Nos. 3,477,822 and 3,540,858. Additionally, many trays have been developed for testing samples photo-optically, which prior art devices are shown in U.S. Pat. Nos. 2,879,141; 3,038,340; 3,041,146; 3,368,872; 3,449,959; 3,469,438; 3,477,821; 3,477,822; 3,480,398; 3,480,399; 3,532,470; 3,540,858; 3,554,704; 3,544,705; 3,574,553; 3,594,129; 3,676,080; 3,690,833; 3,692,487; 3,692,488; 3,704,099; and 3,707,354.
None of the prior art devices were designed for the purposes of enabling a circular cuvette to measure, simultaneously, two samples utilizing a single source of light so that comparable measurements can be had of each sample. Further, it was difficult, if not impossible, to manufacture such a device without warpage of the cuvette in use, which warpage would prevent accurate measurements.
Further, prior art devices did not accurately insure uniform warm-up time for the sample and reagent under all test conditions.